1. Field of the Invention
The present invention refers to a thin-film magnetic head for the magnetic recording device arranged to make up a magnetic core, magnetic gap, coil, and the like by the thin-film formation method and, more particularly, a thin-film magnetic head that can cope with a high recording density by making the magnetic resistance of a magnetic core small.
2. Description of the Related Art
In the magnetic playback device, a slider with a built-in magnetic head as one unit is fixed to the gimbal at the tip of a load arm and the flow of air past the slider as the magnetic disk rotates causes the slider to float above the magnetic disc at a position so that the magnetic head can read/write information from/to the magnetic disk through a magnetic gap at a position of the magnetic head opposed to the magnetic disk.
The floating magnetic head is formed with an electromagnetic converter element integrated in the slider. As an electromagnetic converter element, a type of element with a coil wound on the core, and a thin-film magnetic head with the magnetic core, magnetic gap, coil, and the like fabricated by the thin-film formation method are known.
As shown in FIG. 4, the thin-film magnetic head comprises a bottom magnetic pole layer 12 formed of permalloy, a gap layer 13, a spiral copper coil layer 14, an insulating layer 15, a permalloy top magnetic pole layer 16 in sequence stacked on a ceramic wafer 11, and is so constructed as to have a magnetic gap 17 at the end of the gap layer 13 facing the magnetic recording medium. To form a magnetic circuit of the bottom magnetic pole layer 12, the top magnetic pole layer 16, and the magnetic gap 17, the opposite portion of the top magnetic pole layer 16 to the magnetic gap 17 is magnetically joined to the bottom magnetic pole layer 12. For this joining, as shown in FIG. 5, a hole 18 is bored through a portion of the gap layer 13 and the insulating layer 15 that corresponds to the above joining on the bottom magnetic pole layer 12 and is filled with the formation of the top magnetic pole layer 16 after making the hole 18 so that the top magnetic pole layer 16 is magnetically joined to the bottom magnetic pole layer 12 through the portion of the hole 18.
FIG. 6 is a sectional view taken along the line A--A of FIG. 4. In connection with the width W of the top magnetic pole layer 16, the portion corresponding to the hole is formed with the bottom side width W.sub.2 smaller than the top side width W.sub.1, what is called in a shape of inverse trapezoid, and the magnetic pole layer is stacked on the side face of the hole 18 at the making of the top magnetic pole layer 16 to connect the top magnetic pole layer 16 to the bottom magnetic pole layer 12. On the other hand, the top magnetic pole layer 16 is extended to the position corresponding to the magnetic gap 17 to form a magnetic gap and to constitute a magnetic circuit together with the top magnetic pole layer 16 and the bottom magnetic pole layer 12.
Recently, with increasing density of the magnetic recording, a magnetic head becomes small-sized and correspondingly magnetic pole layers forming the magnetic circuit naturally become smaller. Thus, there is a problem that lowering of the joining area leads to an increase in magnetic resistance though a hole is bored in the gap layer 13 or the insulating layer 15 and the top and bottom magnetic pole layers are magnetically connected at the size of the hole portion.
In addition, the hole 18 for connecting the top magnetic pole layer 16 to the bottom magnetic pole layer 12 is formed in a shape of inverse trapezoid, the magnetic pole layer is difficult to be stacked on the side face of the hole 18, in the worst case does not connect the top and bottom magnetic pole layers, that is, the disconnection between both the magnetic pole layers happens and so the magnetic resistance increases more and more. The smaller the bottom side width W.sub.2 is than the top side width W.sub.1, the easier the magnetic pole layer becomes in being deposited on the side face of the hole 18. However, since it is so constructed that the top side width W.sub.1 is smaller than the width W of the top magnetic pole layer 16, the narrowed W accompanying the small-sized magnetic head makes the bottom side width W.sub.2 smaller increasingly, thereby resulting in an increase in magnetic resistance.
Furthermore, if there is a magnetic material near the coil, a leakage flux increases and consequently a related increase in inductance occurs. And, the stray capacity becomes also larger, thereby worsening the high frequency characteristics. That is, all these are inappropriate to the high recording density. The sectional area of a magnetic circuit can be decreased in inverse proportion to the frequency. The prior art top magnetic pole layer is thicker than is required, covers the coil layer and so had a structure inappropriate for a high frequency application.